In machine tools for cutting workpieces with rotating tools, there is known a machine tool provided with a spindle unit having a tilt shaft for rotating and tilting a spindle to the front end of which a tool is attached, while supporting a spindle head for rotatably driving the spindle by a spindle head support.
Patent Literature 1 describes a machine tool which is provided with the above spindle unit. It discloses, as the drive motors for rotatably driving the tilt shaft, a system which arranges two DD motors (direct drive motors) at the inside of the spindle head support, and connects the motor rotors to the tilt shaft extending from the two side faces of the spindle head without using drive transmission means such as gears to rotatably drive the spindle head. Further, Patent Literature 2 discloses a spindle unit of a type which uses a single motor to transmit rotational drive power to the tilt shaft by two systems.
However, with the configuration in the drive system of a tilt shaft according to the above prior art, there is a problem that a great deal of time is required for replacing a motor. The reason is that, since the configuration of the drive part becomes complicated, a large number of parts have to be detached when changing a motor, and naturally much time is required for assembly.
There is a similar problem in a table unit having a tilt shaft which rotates and tilts a table base for supporting a table to which a workpiece is attached.